The daughter of a daughter isotope is sometimes called a granddaughter isotope.

The time it takes for a single parent atom to decay to an atom of its daughter isotope can vary widely, not only for different parent-daughter chains, but also for identical pairings of parent and daughter isotopes.

While the decay of a single atom occurs spontaneously, the decay of an initial population of identical atoms over time t, follows a decaying exponential distribution, e, where λ is called a decay constant.

Because of this exponential nature, one of the properties of an isotope is its half-life, the time by which half of an initial number of identical parent radioisotopes have decayed to their daughters.